The present invention relates to a chamber cleaning gas and an etching gas More particularly, the invention relates to a chamber cleaning gas suitable for CVD equipment and an etching gas in production of semiconductor devices, wherein both gases comprise a fluorine-containing carbonyl compound having a COF group, and hardly generate substances in the exhaust gases such as CF4, etc, which are harmful to the environment because of being perceived as contributing to global warming.
In conventional production process of thin film devices for semiconductor manufacturing and the like, various thin films and thick films have been formed by CVD process, etc. In forming such thin films on wafers for semiconductor device, thin film materials unfavorably stick to the inner wall of a chamber, jigs supporting an object or pipes in addition to the object to form films. Such deposits induce the cause of contaminating semiconductor products with fine particles, and thereby high quality thin films are hardly prepared and further the yield of the products is lowered. Therefore, the removal thereof is necessary occasionally. Conventionally, the removal of deposits has been conducted manually or by a cleaning gas or the like.
In semiconductors, circuit patterns are formed on various thin film materials constituting semiconductor circuits so that the partial removal of thin film materials has been conducted by gas etching.
With regard to the basic properties required for such cleaning gas or etching gas, the cleaning gas is desired to have a high cleaning rate, and the etching gas is desired to have a high rate of etching objects and high selectivity. The both gases are required not to produce harmful exhaust gases to the environment and to be friendly toward the global environment.
Conventionally, as gases for cleaning such deposits or gases for etching thin films, large amounts of fluorinated compounds such as CF4, C2F6, SF6 or NF3 have been used in processes of manufacturing semiconductors.
These fluorinated compounds, however, are stable compounds having a long atmospheric lifetime, and have a problem in that, after cleaning or etching with these gases, it is difficult to treat un-decomposed gases and the treatment cost thereof is high. These fluorinated compounds, further, have an extremely high global warming potential (100 year integration time horizon) as compared with CO2, for example, CF4 has a global warming potential 6500 times greater than that of CO2, C2F6 has 9200 times, SF6 has 23900 times and NF3 has 8000 times. Therefore, the fluorinated compounds have an uneasy problem of exerting an adverse influence upon the environment. On this account, the development of an alternative gas having a low global warming potential, excellent cleaning properties for silicon-containing deposits of semiconductors and etching properties for silicon-containing films has been desired.
Further, even if the cleaning gas itself has no perceptible influence to the environment, the cleaning gas is decomposed after cleaning or etching with the result that a gas having a long atmospheric lifetime and being environmentally harmful, such as CF4, etc, is occasionally generated. Therefore, the development of alternative gases that decomposed gases thereof exert no adverse influence upon the environment has been desired. In the light of the foregoing, it is an object of the invention to provide a gas for cleaning chambers such as CVD equipment having excellent cleaning properties to silicon-containing deposits being suitable for manufacturing of semiconductors, and an etching gas having etching properties to silicon-containing films, wherein the gases have a low global warming potential, hardly generate substances in the exhaust gases such as CF4, etc which are harmful to the environment and have been perceived as contributing to global warming, and further the gases have excellent exhaust gas treating properties, and easy handling.
The present invention is intended to solve the above problems, and the present inventors found that gases prepared by mixing a specific fluorine-containing carbonyl compound with oxygen have a low global warming potential and hardly generate substances in the exhaust gases such as CF4, etc which are harmful to the environment and largely affect global warming even after cleaning or etching using the gases, and the gases also have excellent cleaning properties to silicon-containing deposits and etching properties to silicon-containing films.
Thus, the present invention has been accomplished. The details are as follows.
The first chamber cleaning gas according to the present invention comprises FCOF and O2, and optionally other gases wherein the total content of FCOF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of FCOF to O2 (FCOF/O2) preferably satisfies the formula 1xe2x89xa6FCOF/O2xe2x89xa69.
The first chamber cleaning gas of the invention may comprise CF3OCOF and O2 and optionally other gases. Further, the first chamber cleaning gas may comprise CF3OCF2OCOF and O2, and optionally other gases.
Further, the first chamber cleaning gas of the invention may comprise at least one fluorine compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2, and optionally other gases, wherein the total content of O2 and at least one fluorine compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The second chamber cleaning gas of the invention comprises CF3COF and O2, and optionally other gases, wherein the total content of CF3COF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of CF3COF to O2 (CF3COF/O2) preferably satisfies the formula 0.25xe2x89xa6CF3COF/O21.5.
The second chamber cleaning gas of the invention may comprise C3F7COF and O2, and optionally other gases, wherein the total content of C3F7COF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %, and further, the second chamber cleaning gas may comprise CF2(COF)2 and O2 and optionally, other gases wherein the total content of CF2(COF)2 and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The other gases preferably comprises at least one inert gas selected from N2, He, Ne, Ar, Kr, Xe and Rn.
When the chamber cleaning gas contains FCOF, the other gases may contain CF3OCOF and/or CF3OCF2OCOF.
The chamber cleaning gas is preferably a gas for cleaning chambers of CVD equipment.
The chamber cleaning gas is preferably a gas for cleaning silicon-containing deposits, and the silicon-containing deposits preferably comprise at least one of (1) silicon, (2) a compound comprising silicon and at least one of oxygen, nitrogen, fluorine and carbon, and (3) a compound of a metal silicide having a high melting point.
The first etching gas for silicon-containing films according to the present invention comprises FCOF and O2, and optionally other gases wherein the total content of FCOF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of FCOF to O2 (FCOF/O2) preferably satisfies the formula 1xe2x89xa6FCOF/O2xe2x89xa69.
The first etching gas for silicon-containing films of the present invention may comprise CF3OCOF and O2, and optionally other gases. Further, the first etching gas for silicon-containing films comprises CF3OCF2OCOF and O2, and optionally other gases.
Further, the first etching gas for silicon-containing films may comprise at least one fluorine compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2, and optionally other gases, wherein the total content Of O2 and at least one fluorine compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The second etching gas for silicon-containing films of the present invention comprises CF3COF and O2, and optionally other gases, wherein the total content of CF3COF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of CF3COF to O2 (CF3COF/O2) preferably satisfies the formula 0.25xe2x89xa6CF3COF/O2xe2x89xa61.5.
The second etching gas for silicon-containing films of the present invention may comprise C3F7COF and O2, and optionally other gases, wherein the total content of C3F7COF and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %. Further, the second etching gas for silicon-containing films may comprise CF2(COF)2 and O2, and optionally other gases, wherein the total content of CF2(COF)2 and O2 is in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The other gases preferably comprise at least one inert gas selected from N2, He, Ne, Ar, Kr, Xe and Rn.
When the etching gas for silicon-containing films contains FCOF, the other gases may contain CF3OCOF and/or CF3OCF2OCOF.
The silicon-containing films preferably comprise at least one of (1) a silicon film, (2) a film comprising silicon and at least one of oxygen, nitrogen, fluorine and carbon, and (3) a film of a metal silicide having a high melting point.
The chamber cleaning gas for silicon-containing deposits and the etching gas for silicon-containing films of the present invention are gases prepared by mixing a specific fluorine-containing carbonyl compound having a COF group with oxygen. Each gas will be described hereinafter.
[Chamber Cleaning Gas]
The first chamber cleaning gas of the present invention is a cleaning gas comprising at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF.
The second chamber cleaning gas of the present invention is a chamber cleaning gas comprising CF3COF, C3F7COF or CF2(COF)2.
These will be described in order hereinafter.
 less than A Cleaning Gas Comprising at Least One Compound Selected From the Group Consisting of FCOF, CF3OCOF and CF3OCF2OCOF greater than 
The first chamber cleaning gas of the invention is a cleaning gas comprising at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF.
Of these, FCOF is preferably used.
In the use of FCOF, the chamber cleaning gas comprises FCOF and O2, and optionally other gases and the total content of FCOF and O2 is desirably in the range of 70 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of FCOF to O2 (FCOF/O2) desirably satisfies 1xe2x89xa6FCOF/O2xe2x89xa69, preferably 1.5xe2x89xa6FCOF/O2xe2x89xa66, more preferably 2.3xe2x89xa6FCOF/O2xe2x89xa66.
In the chamber cleaning gas containing FCOF, examples of the other gases optionally contained may include an inert gas such as N2, He, Ne, Ar, Kr, Xe and Rn. The inert gas may be used alone or in a mixed gas with two or more.
The chamber cleaning gas containing FCOF may contain the other gases, for example, CF3OCOF and/or CF3OCF2OCOF.
Such CF3OCOF and CF3OCF2OCOF are compounds obtainable as a mixture together with FCOF through preparation processes and preparation conditions. When they are prepared in a mixture, they can be separated by conventionally known processes such as distillation, and further the mixture can be used as the chamber cleaning gas.
When CF3OCOF is used as the chamber cleaning gas of the invention without the use of FCOF and CF3OCF2OCOF, the chamber cleaning gas may comprise CF3OCOF and O2, and optionally the other gases.
The mixing molar ratio of CF3OCOF to O2 (CF3OCOF/O2) satisfies preferably 0.4xe2x89xa6CF3OCOF/O2xe2x89xa69, more preferably 0.5xe2x89xa6CF3OCOF/O2xe2x89xa66, furthermore preferably 0.6xe2x89xa6CF3OCOF/O2xe2x89xa64.
When CF3OCF2OCOF is used as the chamber cleaning gas of the invention without the use of FCOF and CF3OCOF, the chamber cleaning gas may comprise CF3OCF2OCOF and O2, and optionally the other gases.
In this case, the mixing molar ratio of CF3OCF2OCOF to O2 (CF3OCF2OCOF/O2) satisfies preferably 0.25xe2x89xa6CF3OCF2OCOF/O2xe2x89xa69, more preferably 0.3xe2x89xa6CF3OCF2OCOF/O2xe2x89xa64, furthermore preferably 0.4xe2x89xa6CF3OCF2OCOF/O2xe2x89xa62.5.
When the first chamber cleaning gas of the invention comprises at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2, and optionally other gases, the total content of FCOF and O2 is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
When the first chamber cleaning gas of the invention has the gas content and mixing molar ratio as described in the above, it is possible to attain the cleaning rate same as that of C2F6 used conventionally and also remove deposits adhered to chambers quickly.
Further, the exhaust gases evacuated after chamber cleaning contain by-products generated by decomposition of the cleaning gas. For example, the chamber cleaning is carried out using C2F6 as described in the above, the exhaust gas contains CF4 having a long atmospheric lifetime of 50000 years and a high global warming potential. However, when the first chamber cleaning gas comprising FCOF and O2 of the invention is used, it is possible to attain the cleaning rate same as that of C2F6 and also pronouncedly reduce the CF4 content in the exhaust gas as compared with the use of C2F6.
The above described FCOF, CF3OCOF and CF3OCF2OCOF used in the present invention easily react with moisture to decompose into HF and CO2. On this account, even if FCOF, CF3OCOF and/or CF3OCF2OCOF are discharged as un-decomposed exhaust gases after chamber cleaning, they can be easily decomposed into HF and CO2 by a water scrubber of a conventional exhaust gas treatment system. So it is unnecessary for post treatment to use an additional combustion decomposition apparatus and thereby the system cost can be reduced.
Moreover, even if the gas is discharged in the atmosphere, it easily decomposes together with moisture in the atmosphere. The atmospheric lifetime thereof is estimated to be 1 year or less and the global warming potential thereof is considered to be the same as that of CO2, which potential is much lower than that of CF4. Therefore, it is considered the effect thereof on global warming is low.
FCOF has a low boiling point of xe2x88x9283.1xc2x0 C. and is in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in chamber cleaning.
Further, for example, CF3OCOF has a boiling point of xe2x88x9234xc2x0 C. and CF3OCF2OCOF has a boiling point of +7xc2x0 C., and they are in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in chamber cleaning similar to FCOF.
The FCOF preparation process is not particularly limited, for example, comprises allowing carbon monoxide to react with a fluorine gas.
The CF3OCOF and CF3OCF2OCOF preparation processes are not particularly limited, and may include conventionally known processes e.g. a process disclosed in U.S. Pat. No. 3,721,696. For example, CF3OCOF and CF3OCF2OCOF can be prepared by allowing C3F6 to react with oxygen gas. The resulting compound, which depends on preparation conditions, can be prepared in a mixture of the above FCOF, CF3OCOF or CF3OCF2OCOF.
 less than Cleaning Gas Containing CF3COF, C3F7COF or CF2(COF)2 greater than 
The second chamber cleaning gas of the present invention comprises CF3COF, C3F7COF or CF2(COF)2, and O2 and optionally other gases. Examples of the other gases used in the invention may include an inert gas such as N2, He, Ne, Ar, Kr, Xe and Rn. The inert gas may be used alone or in a mixed gas of two or more.
In the use of CF3COF as the second chamber cleaning gas of the invention, the total amount of CF3COF and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second chamber cleaning gas of the invention has a mixing molar ratio of CF3COF to O2 (CF3COF/O2) satisfies preferably 0.25xe2x89xa6CF3COF/O2xe2x89xa61.5, more preferably 0.4xe2x89xa6CF3COF/O2xe2x89xa61, furthermore preferably 0.5xe2x89xa6CF3COF/O2xe2x89xa60.8.
When the second chamber cleaning gas of the invention has the CF3COF content, the O2 content, the other gas content and the mixing molar ratio of CF3COF to O2 as described in the above, it is possible to attain about 70% of the cleaning rate of C2F6 used conventionally and also remove deposits adhered to chambers quickly.
In the use of C3F7COF as the second chamber cleaning gas of the invention, the total amount of C3F7COF and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second chamber cleaning gas of the invention has a mixing molar ratio of C3F7COF to O2 (C3F7COF/O2) satisfies preferably 0.1xe2x89xa6C3F7COF/O2xe2x89xa60.7, more preferably 0.15xe2x89xa6C3F7COF/O2xe2x89xa60.6, furthermore preferably 0.25xe2x89xa6C3F7COF/O2xe2x89xa60.5.
When the second chamber cleaning gas of the invention has the C3F7COF content, the O2 content, the other gas content and the mixing molar ratio of C3F7COF to O2 as described in the above, it is possible to attain about 70% of the cleaning rate of C2F6 used conventionally and also remove deposits adhered to chambers quickly.
In the use of CF2(COF)2 as the second chamber cleaning gas of the invention, the total amount of CF2(COF)2 and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second chamber cleaning gas of the invention has a mixing molar ratio of CF2(COF)2 to O2 (CF2(COF)2/O2) satisfies preferably 0.15xe2x89xa6CF2(COF)2/O2xe2x89xa61.3, more preferably 0.25xe2x89xa6CF2(COF)2/O2xe2x89xa61, furthermore preferably 0.3xe2x89xa6CF2(COF)2/O2xe2x89xa60.85.
When the second chamber cleaning gas of the invention has the CF2(COF)2 content, the O2 content, the other gas content and the mixing molar ratio of CF2(COF)2 to O2 as described in the above, it is possible to attain about 70% of the cleaning rate of C2F6 used conventionally and also remove deposits adhered to chambers quickly.
Further, the exhaust gas evacuated after chamber cleaning contains by-products generated by decomposition of the cleaning gas. For example, the chamber cleaning is carried out using C2F6 as described in the above, the exhaust gas contains CF4 having a long atmospheric lifetime of 50000 years and a high global warming potential. However, when the second chamber cleaning gas containing CF3COF, C3F7COF or CF2(COF)2, and O2 of the invention is used, it is possible to attain about 70% of the cleaning rate of C2F6 and also reduce the CF4 content in exhaust gas as compared with the use of C2F6.
The CF3COF, C3F7COF and CF2(COF)2 used in the present invention easily react with moisture to decompose into HF and CF3COOH. On this account, even if CF3COF, C3F7COF and CF2(COF)2 are discharged as un-decomposed exhaust gas after chamber cleaning, they can be easily decomposed into HF and CF3COOH by a water scrubber of a conventional exhaust gas treatment system. So it is unnecessary for post treatment to use an additional combustion decomposition apparatus and thereby the system cost can be reduced.
Moreover, even if the exhaust gases are discharged in the atmosphere, they easily react with moisture in the atmosphere to decompose. The atmospheric lifetime thereof is estimated to be 1 year or less and the global warming potential thereof is much lower than that of CF4, etc. Therefore, it is considered the effect thereof on global warming is low.
CF3COF has a boiling point of xe2x88x9259xc2x0 C., C3F7COF has a boiling point of 2 to 5xc2x0 C. and CF2(COF)2 has a boiling point of xe2x88x928xc2x0 C., so that every boiling point is low. They are each in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in chamber cleaning.
The CF3COF preparation process used in the present invention is not particularly limited, for example, comprises allowing trifluoroethanol (CF3CH2OH) to react with fluorine gas.
The C3F7COF preparation process used in the invention is not particularly limited, and may include known processes, for example, a process of electrolysis fluorination of C3H7COF. Further, commercially available C3F7COF is also employable.
The CF2(COF)2 preparation process used in the invention is not particularly limited, and may include known processes. For example, it is prepared by allowing CH2(COF)2 and NaF to react with fluorine gas.
 less than Other Optional Components greater than 
The above other gases may include gases other than the above inert gases within the limit of not missing the object of the invention. Examples of the gases other than the inert gases may include O3, H2, F2, ClF3 or BrF3.
 less than Chamber Cleaning greater than 
The chamber cleaning used in the present invention means removing deposits adhered to chamber walls, jigs or pipes in a semiconductor manufacturing apparatus such as CVD equipment, etc.
The mixed gas containing the above fluorine-containing carbonyl compound, oxygen and the like can be used as the gas for cleaning chambers of CVD equipment, etc.
The objective compounds applicable for the chamber cleaning with the fluorine-containing carbonyl compound may include the above silicon-containing deposits (deposits containing silicon) adhered to the wall of a CVD chamber or jigs of CVD equipment by CVD processes or the like. The silicon-containing deposits may comprise for example, at least one of:
(1) silicon
(2) a compound of silicon and at least one of oxygen, nitrogen, fluorine and carbon, and
(3) a compound of a metal silicide having a high melting point. Specific examples thereof may include the metal silicide having a high melting point such as WSi, etc, and Si, SiO2 and Si3N4.
The materials of the chambers for which the chamber cleaning gases of the present invention are used are not particularly limited, and for example, may include conventionally known materials. Examples of such chamber materials may include stainless steel, aluminum or alloys thereof.
The chamber cleaning gases of the invention exert a little effect such as corrosion on such chambers so that the above deposits adhered to the chambers can be removed selectively and quickly.
For cleaning silicon-containing deposits in chambers using such fluorine compounds of the invention, conventionally known processes can be employed. Applicable examples thereof may include various dry cleaning methods such as plasma cleaning, remote plasma cleaning or microwave cleaning.
The use of the chamber cleaning gases of the present invention enables to remove silicon-containing deposits.
[Etching Gas for Silicon-Containing Films]
The first etching gas for silicon-containing films of the present invention is an etching gas for silicon-containing films comprising at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF.
The second etching gas for silicon-containing films of the present invention is an etching gas for silicon-containing films comprising CF3COF, C3F7COF or CF2(COF)2.
These will be described in order hereinafter.
 less than Etching Gas for Silicon-Containing Films Comprising at Least One Compound Selected From the Group Consisting of FCOF, CF3OCOF and CF3OCF2OCOF greater than 
The first silicon-containing film etching gas of the invention is a silicon-containing film etching gas comprising at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF.
Of these, FCOF is preferably used.
In the use of FCOF, the silicon-containing film-etching gas comprises FCOF and O2, and optionally other gases and the total content of FCOF and O2 is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
The mixing molar ratio of FCOF to O2 (FCOF/O2) desirably satisfies 1xe2x89xa6FCOF/O2xe2x89xa69, preferably 1.5xe2x89xa6FCOF/O2xe2x89xa66, more preferably 2.3xe2x89xa6FCOF/O2xe2x89xa66.
In the silicon containing film-etching gas containing FCOF, the other gases include, for example, an inert gas such as N2, He, Ne, Ar, Kr, Xe and Rn. The inert gas may be used alone or in a mixed gas with two or more.
The silicon containing film-etching gas containing FCOF may contain the other gases, for example, CF3OCOF and/or CF3OCF2OCOF.
Such CF3OCOF and CF3OCF2OCOF are compounds obtainable as a mixture together with FCOF through preparation processes and preparation conditions in some cases. When they are prepared in a mixture, they can be separated by conventionally known processes such as distillation, and further the mixture can be used as the silicon containing film-etching gas.
When CF3OCOF is used as the silicon containing film-etching gas of the invention without the use of FCOF and CF3OCF2OCOF, the silicon containing film-etching gas may comprise CF3OCOF and O2, and optionally the other gases.
The mixing molar ratio of CF3OCOF to O2 (CF3OCOF/O2) satisfies preferably 0.4xe2x89xa6CF3OCOF/O2xe2x89xa69, more preferably 0.5xe2x89xa6CF3OCOF/O2xe2x89xa66, furthermore preferably 0.6xe2x89xa6CF3OCOF/O2xe2x89xa64.
When CF3OCF2OCOF is used as the silicon containing film-etching gas of the invention without the use of FCOF and CF3OCOF, the silicon containing film-etching gas may comprise CF3OCF2OCOF and O2, and optionally the other gases.
The mixing molar ratio of CF3OCF2OCOF to O2 (CF3OCF2OCOF/O2) satisfies preferably 0.25xe2x89xa6CF3OCF2OCOF/O2xe2x89xa69, more preferably 0.3xe2x89xa6CF3OCF2OCOF/O2xe2x89xa64, furthermore preferably 0.4xe2x89xa6CF3OCF2OCOF/O2xe2x89xa62.5.
When the first silicon containing film-etching gas of the invention comprises at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2, and optionally other gases, the total content of FCOF and O2 is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
When the first silicon containing film-etching gas of the invention has the gas content and mixing molar ratio as described in the above, it is possible to attain the etching rate same as that of C2F6 used conventionally.
Further, when the etching is carried out using C2F6 as described in the above, the exhaust gas contains CF4 having a high global warming potential as byproducts. However, when the first silicon containing film-etching gas comprising at least one compound of FCOF, CF3OCOF and CF3OCF2OCOF, and O2 of the invention is used, it is possible to attain the etching rate same as that of C2F6 and also pronouncedly reduce the CF4 content in the exhaust gas as compared with the use of C2F6.
The FCOF used in the present invention reacts with moisture easily to decompose into HF and CO2. On this account, the decomposition treatment is easily conducted thereby reducing the system cost.
Moreover, even if the exhaust gas is discharged in the atmosphere, it easily reacts with moisture in the atmosphere to decompose. Therefore, it is considered the effect thereof on global warming is low.
As described in the above, FCOF has a low boiling point of xe2x88x9283.1xc2x0 C. and is in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in etching. Further, CF3OCOF has a boiling point of xe2x88x9234xc2x0 C. and CF3OCF2OCOF has a boiling point of +7xc2x0 C., and they are in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in the silicon containing film etching, similar to FCOF.
The FCOF, CF3OCOF and CF3OCF2OCOF preparation processes and accesses are the same as the above-described processes. The first etching gas of the invention has good selectivity to films for processing and thereby is sufficiently applicable as alternating gases for C2F6, etc.
 less than Etching Gas Containing CF3COF greater than 
The second silicon-containing film etching gas of the present invention comprises CF3COF, C3F7COF or CF2(COF)2, and O2 and optionally other gases. Examples of the other gases used in the invention may include an inert gas such as N2, He, Ne, Ar, Kr, Xe and Rn. The inert gas may be used alone or in a mixed gas of two or more.
In the use of CF3COF as the second silicon containing film-etching gas of the invention, the total amount of CF3COF and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second silicon containing film-etching gas has a mixing molar ratio of CF3COF to O2 (CF3COF/O2) satisfies preferably 0.25xe2x89xa6CF3COF/O2xe2x89xa61.5, more preferably 0.4xe2x89xa6CF3COF/O2xe2x89xa61, furthermore preferably 0.5xe2x89xa6CF3COF/O2 greater than 0.8.
When the second silicon containing film-etching gas of the invention has the CF3COF content, the O2 content, the other gas content and the mixing molar ratio of CF3COF to O2 as described in the above, it is possible to attain about 70% of the etching rate of C2F6 used conventionally.
In the use of C3F7COF as the second silicon containing film-etching gas of the invention, the total amount of C3F7COF and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second silicon containing film-etching gas has a mixing molar ratio of C3F7COF to O2 (C3F7COF/O2) satisfies preferably 0.1xe2x89xa6C3F7COF/O2xe2x89xa60.7, more preferably 0.15xe2x89xa6C3F7COF/O2xe2x89xa60.6, furthermore preferably 0.1xe2x89xa6C3F7COF/O2xe2x89xa60.5.
When the second silicon containing film-etching gas of the invention has the C3F7COF content, the O2 content, the other gas content and the mixing molar ratio of C3F7COF to O2 as described in the above, it is possible to attain about 70% of the etching rate of C2F6 used conventionally and also remove deposits adhered to chambers quickly.
In the use of CF2(COF)2 as the second silicon containing film-etching gas of the invention, the total amount of CF2(COF)2 and O2 molar concentration is desirably in the range of 70 to 100 mol %, preferably 80 to 100 mol % based on the total gas amount being 100 mol %.
Further, the second silicon-containing film etching gas of the invention has a mixing molar ratio of CF2(COF)2 to O2 (CF2(COF)2/O2) satisfies preferably 0.15xe2x89xa6CF2(COF)2/O2xe2x89xa61.3, more preferably 0.25xe2x89xa6CF2(COF)2/O2xe2x89xa61, furthermore preferably 0.3xe2x89xa6CF2(COF)2/O2xe2x89xa60.85.
When the second silicon containing film-etching gas of the invention has the CF2(COF)2 content, the O2 content, the other gas content and the mixing molar ratio of CF2(COF)2 to O2 as described in the above, it is possible to attain about 70% of the etching rate of C2F6 used conventionally.
Further, when the etching is carried out using C2F6 as described in the above, the exhaust gas contains CF4 having a long atmospheric lifetime of 50000 years and a high global warming potential. However, when the second silicon containing film-etching gas containing CF3COF, C3F7COF or CF2(COF)2, and O2 of the invention is used, it is possible to attain about 70% of the etching rate of C2F6 and also reduce the CF4 content in the exhaust gas as compared with the use of C2F6.
The above described CF3COF, C3F7COF and CF2(COF)2 used in the present invention easily react with moisture to decompose into HF and CF3COOH. On this account, even if CF3COF, C3F7COF and CF2(COF)2 are discharged as un-decomposed exhaust gas after etching, they can easily decompose into HF and CF3COOH by a water scrubber which is a conventional exhaust gas treatment system and it is unnecessary for post treatment to use an additional combustion decomposition apparatus and thereby the system cost can be reduced.
Moreover, even if the exhaust gas is discharged in the atmosphere, they easily react with moisture in the atmosphere to decompose. The atmospheric lifetime thereof is estimated to be 1 year or less and the global warming potential thereof is much lower than that of CF4, etc. Therefore, it is considered the effect thereof on global warming is low.
Further, CF3COF has a boiling point of xe2x88x9259xc2x0 C., C3F7COF has a boiling point of 2 to 5xc2x0 C. and CF2(COF)2 has a boiling point of xe2x88x928xc2x0 C., so that every boiling point is low. They are each in a gas state under conditions of semiconductor manufacturing so that the handling thereof is easy in etching.
The CF3COF, C3F7COF and CF2(COF)2 preparation processes and accesses are the same as in the above-described processes. The second etching gas of the invention has good selectivity to films for processing and thereby is sufficiently applicable as alternating gases for C2F6, etc.
 less than Other Optional Components greater than 
The above other gases may include gases other than the above inert gases within the limit of not missing the object of the invention. Examples of the gases other than the inert gases may include O3, H2, F2, ClF3 or BrF3.
 less than Etching greater than 
The objective compounds applicable for the etching may include silicon-containing films (films containing silicon) or the like. The silicon-containing films may include, for example, at least one of:
(1) a silicon film
(2) a film of silicon and at least one of oxygen, nitrogen, fluorine and carbon, and
(3) a film of a metal silicide having a high melting point. Specific examples thereof may include Si film, SiO2 film, Si3N4 film or metal silicides having a high melting point such as WSi film.
The process of etching the silicon-containing films with the fluorine-containing carbonyl compound of the present invention may include conventionally known processes.
Applicable examples thereof may include various dry etching methods such as plasma etching, reactive ion etching or microwave etching. For the silicon-containing film etching conditions, known etching conditions are applicable.
The chamber cleaning gas of the present invention which comprises the above gases in a specific proportion has the almost same excellent cleaning rate as that of conventionally used C2F6 And also the chamber cleaning gas of the invention has a low global warming potential and can remarkably reduce the CF4 generation wherein CF4 is an exhaust gas being harmful to the environment and being perceived as contributing to global warming after cleaning by use of the gas. The chamber cleaning gas of the present invention, further, has easy handling and excellent exhaust gas treating properties thereby enhancing economic properties and workability for the chamber cleaning.
The etching gas for silicon-containing films of the present invention which comprises the above gases in a specific proportion has the almost same excellent etching rate as that of conventionally used C2F6 And also the etching gas for silicon-containing films of the present invention has a low global warming potential and can remarkably reduce the CF4 generation wherein CF4 is an exhaust gas being harmful to the environment and being perceived as contributing to global warming after etching by use of it. The etching gas of the present invention, further, has easy handling and excellent exhaust gas treating properties thereby enhancing economic properties and workability for the etching. The etching by use of the gas enables to remove silicon-containing films efficiently and further the etching can be performed while keeping the dimensional accuracy of semiconductor patterns high so that the etching gas of the invention has excellent etching properties.